Mate fidelity in an Australian lizard Trachydosaurus rugosus

Summary The Australian sleepy lizard Trachydosaurus rugosus is a large mainly herbivorous skink, which occupies overlapping home ranges. In the Mt. Mary study area, South Australia, 6567 captures were made of 2412 different individuals between February 1982 and December 1986. The mating season when male and female lizards formed pairs was in the spring months of October and November. Some lizards were captured in pairs more than once in the same mating season. Amongst this group over 90% of females and over 70% of males were found with the same partner. These monogamous pair-bonds lasting up to eight weeks, had been predicted by Stamps (1983) for large lizards with overlapping home ranges. In addition 79% of females and 68% of males recaptured in pairs in subsequent years were found with the same partner. This mate fidelity is too high to be accounted for by chance encounters. The selective advantages of actively choosing the same partner each year are discussed.